When Abby is talking to the pregnant woman about getting an abortion, her arms alternate between being at her side and being crossed in between shots when the camera is behind her.
When Mark Greene starts his dinner with his father the slab of butter is whole but then is missing a corner when Mark first removes some with his knife, a sign a previous take was done.
When Dr. Weaver is suspended, the white board with patients on it has the initials "KW" on it, even though she has been gone for a few days.